# Search results

1. ### The relationship between the lattice spacing and the distance between parallel planes

How can one derive the relationship for a cubic crystal: d= \frac{a}{\sqrt{h^2 + k^2 + l^2}} It is shown here. This is probably trivial but I am having trouble proving it as the Miller indices are reciprocals but the reciprocal is not distributive. This isn't for homework by the way - I...
2. ### Where can I find theoretical isochrones?

I am currently doing a 2nd year lab report and need some theoretical isochrones to work out the age of some clusters, M15 and H+chi persei (Double Cluster). I was going to use Seiss: http://www-astro.ulb.ac.be/~siess/server/iso.html [Broken] But it doesn't seem to be online :( What...
3. ### The treatment of errors and uncertainties?

I am confused over how to work with errors and uncertainties. So far when dealing with a small number of measurements I have used the partial derivative method to calculate the final error in my result e.g. if my result is E=mgh \text{ then assuming no error in g my uncertainty is }...
4. ### Programs How easy is it to find funding to do an Applied Physics PhD abroad?

Although I am not yet sure which area I would want to do a PhD in (I am only in 2nd year undergrad) it would most likely be something applied like accelerator physics, plasma physics, metamaterials, plasmonics etc. (I realise this is a ridiculous range of topics :P ) The proposed ~30% cuts to...
5. ### Please explain what a Fourier transform is?

I understand Fourier Series fairly well and how to use them to approximate functions (I even wrote a C program to do it) but Transforms are really confusing. If I was to take the value of each fourier coefficient and plot it on the y-axis against the angular frequency on x-axis (obv. there...
6. ### Thermodynamics (Adiabatic PV Diagram)

Homework Statement Give a definition of an adiabatic process. Derive an expression for the work performed by n mol of an ideal gas undergoing an adiabatic expansion in terms of the initial and the final temperature of the gas. [Hint: you may find it helpful to apply the First Law to the...
7. ### Simple vectors question that I can't seem to get right?

All information pertaining to the question and my attempted solution is here: http://mathbin.net/39295 [Broken]
8. ### Repulsive Casimir Forces

I need to do a basic talk for a few minutes on Casimir forces and their effects on nanotechnology. I kind of understand the basic concept of Casimir forces intuitively, as less virtual particles can exist in the standing wave state between the plates than can exist outside of the plates and...
9. ### Energy-Time Uncertainty Problem.

Homework Statement Following a question that asks for the Energy-Time uncertainty principle, \Delta E \Delta T \geq \frac{\hbar}{2} Show that for any wave, the fractional uncertainty in wavelength, \frac{\Delta \lambda}{\lambda} is the same in magnitude as the fractional uncertainty in...
10. ### Simple Energy Levels confusion

In the famous diagrams of the energy levels of a hydrogen atom it seems that the energy levels get closer together as they increase such that the difference in energy between higher energy levels is less than between lower ones. But working from the electron in a box approach we get the...
11. ### Inclined Pulley system, little information given.

Homework Statement I have dutifully reproduced the problem in OODraw please forgive the poor aesthetic quality but I believe all the important information is visible. Homework Equations mgL-Lsin(\theta)m'g = \frac{mv^2}{2} + \frac{m'v'^2}{2} T=T' v=v' \therefore v^2 =...
12. ### Travel Opportunities as a Physicist?

As a Physicist (I was thinking mainly about those employed in academia which is why I posted this here and not in Careers Guidance) how much opportunity is there to travel? Many publications by the IoP to encourage students to study physics emphasize the international nature of a research...
13. ### Programs Will my undergrad affect my choice of PhD? (UK)

I'm terribly sorry if this has been asked before, but at the moment I want to work in Nuclear Fusion eventually, MCF like JET etc. seems the most interesting although ICF like NIF is pretty interesting too.. However, many people change their mind over what they want to study whilst they are...
14. ### Please explain binding energy?

Can some kind person please explain why He-4 is so high and Li-6 is so low on the graph of binding energy per nucleon. Copy of the graph here http://en.wikipedia.org/wiki/File:Binding_energy_curve_-_common_isotopes.svg" [Broken] It means that He-4 must be very stable right? Because binding...
15. ### Building an electrolaser

I'm sorry about posting this here.. it's not homework don't worry :tongue2: But I just feel that there must be a more specific subthread for it than general physics, but nevertheless I suppose a moderator can move it if they are aware of such a subthread? Anyway onto the actual thread...
16. ### How important are individuals?

Do you believe that individuals may have a great effect upon the course of science and history in general as proposed by the 'Great man' theory? Or do you subscribe to Tolstoy's views that history is shaped by events that would have come about in any case regardless of the existence of a few...
17. ### Why is CERN better known than ITER?

I find it surprising that whilst the average person will know about CERN, due to its heavy coverage in the news and media, only very few people will have heard of ITER. This seems strange because ITER will probably have a much greater effect upon the average person's life than anything that may...
18. ### Schools How much effect does undergrad university have on choice of PhD uni (UK)?

I am just coming into Year 13 in the UK and I need to choose which universities to apply to, at AS Level I got 5As in Maths, Further Maths, Bio, Chem and Physics so I have a free choice as far as entry requirements go with the exception of places like Oxbridge and maybe even Imperial where there...